# Restarts¶

The main results of a BAND calculation are stored in the rkf file. If you save this file you can use it to restart your calculation. The input for the restart calculation is essentially the same, except for some extra keys, like `Restart`

, `Grid`

, and `DensityPlot`

.

Plots of the density (and many other symmetric properties) can can be obtained with the key `DensityPlot`

. Density and orbital plot restarts require the specification of the `Grid`

key.
With the subkey `SCF`

you can start the SCF procedure with the last solution from the restart file. This can be useful if the SCF did not converge or if you want to compute some post-SCF properties (e.g. the DOS or the band structure). Similarly, a geometry optimization can be restarted with the subkey `GeometryOptimization`

You can use the geometry of a previous calculation.

Usually the input for a restarted job is the same as for the original calculation, with some extra options, described in this section.

Some examples are available in the `$AMSHOME/examples/band`

directory and are discussed in the Examples section.

Example: Restart SCF for properties calculation |

Example: Restart the SCF |

Example: Properties on a grid |

## Restart key¶

```
Restart
File string
SCF Yes/No
DensityPlot Yes/No
OrbitalPlot Yes/No
NOCVdRhoPlot Yes/No
NOCVOrbitalPlot Yes/No
UseDensityMatrix Yes/No
End
```

`Restart`

Type: Block Description: Tells the program that it should restart with the restart file, and what to restart. `File`

Type: String Default value: Description: Name of the restart file. `SCF`

Type: Bool Default value: No GUI name: Restart: SCF Description: Continue the SCF procedure using the orbital coefficients and occupations from the restart file. `DensityPlot`

Type: Bool Default value: No Description: Goes together with the DensityPlot block and Grid blocks `OrbitalPlot`

Type: Bool Default value: No Description: Goes together with the OrbitalPlot and Grid `NOCVdRhoPlot`

Type: Bool Default value: No Description: Goes together with the NOCVdRhoPlot and Grid blocks. `NOCVOrbitalPlot`

Type: Bool Default value: No Description: Goes together with the NOCVOrbitalPlot and Grid blocks. `UseDensityMatrix`

Type: Bool Default value: No Description: If set to True: For restarting the SCF the density matrix will be used. Requires you to set ‘Save DensityMatrix’ in the previous run.

## Grid¶

The Grid block is used for restart options `OrbitalPlot`

, `DensityPlot`

, `NOCVOrbitalPlot`

and `NOCVdRhoPlot`

. There are two ways to define your grid. The most easy way is to use the Type key, which automatically generates a grid around the atoms in the unit cell:

```
Grid
Type [coarse | medium | fine]
End
```

`Grid`

Type: Block Description: Options for the regular grid used for plotting (e.g. density plot). Used ICW the restart option. `Type`

Type: Multiple Choice Default value: coarse Options: [coarse, medium, fine] Description: The default regular grids.

One alternative is to specify everything by hand via the ‘UserDefined’ sub-block.

```
Grid
UserDefined # Non-standard block. See details.
...
End
End
```

`Grid`

Type: Block Description: Options for the regular grid used for plotting (e.g. density plot). Used ICW the restart option. `UserDefined`

Type: Non-standard block Description: Once can define the regular grid specification in this block. See example.

The following input would create a cube from (-1,-1,-1) to (1,1,1):

```
Grid
UserDefined
-1 -1 -1 ! Starting point
1 0 0 0.1 ! vec1 and dvec1
0 1 0 0.1 ! vec2 and dvec2
0 0 1 0.1 ! vec3 and dvec3
20 20 20 ! nr. of steps along three directions
End
End
```

One can also specify a text file from which the grid is imported:

```
Grid
FileName string
End
```

`Grid`

Type: Block Description: Options for the regular grid used for plotting (e.g. density plot). Used ICW the restart option. `FileName`

Type: String Default value: Description: Read in the grid from a file. The file format of the grid is: three numbers per line (defining the x, y and z coordinates of the points).

## Plots of the density, potential, and many more properties¶

```
DensityPlot # Non-standard block. See details.
...
End
```

`DensityPlot`

Type: Non-standard block Description: Plots of the density. Goes together with the Restart%DensityPlot and Grid keys.

The DensityPlot block goes together with the `Restart%DensityPlot`

and `Grid`

keys. Example input:

```
...
Restart
File my_file.rkf
DensityPlot
End
Grid
Type Coarse
End
DensityPlot
rho(fit)
vxc[rho]
End
...
```

After such a run you get a TAPE41 file that you should rename to my.t41, and view with AMSview.

The most common properties to plot are:

`rho(fit)`

The fitted density.`v(coulomb)`

The Coulomb potential.`vxc[rho(fit)]`

the XC potential (using the fitted density)`vxc[rho]`

XC potential of the exact density`rho`

The density`|gradRho|`

The norm of the gradient of the density`tau`

The symmetric kinetic energy density`LDOS`

The local density of states. (See LDOS key)`elf[rho]`

The electron localization function`X`

The Electron energy density function. Equivalently`X(fit)`

may be used as an approximation, employing the density fit.

Some more specialized options are:

`rho(deformation/fit)`

the fitted deformation density`rho(atoms)`

The density of the startup atoms`v(coulomb/atoms)`

The Coulomb potential of the start density`s[rho]`

Reduced density gradient. Common ingredient for XC functionals`s[rho(fit)]`

Same as above, now for the fit density`alpha[rho]`

Ingredient for some meta-GGAs

In the BAND example directory there is the Frags_COCu example which shows how this can be used in combination with the `Fragment`

key.

## Orbital plots¶

```
OrbitalPlot # Non-standard block. See details.
...
End
```

`OrbitalPlot`

Type: Non-standard block Description: Goes together with the Restart%OrbitalPlot and Grid keys. See Example.

The OrbitalPlot block goes together with the `Restart%OrbitalPlot`

and `Grid`

keys. Example input:

```
...
Restart
File my_file.rkf
OrbitalPlot
End
Grid
Type Coarse
End
OrbitalPlot
1 Band 5 8 ! for k-point 1 plot bands 5 to 8
5 Band 6 ! for k-point 5 plot band 6
6 -0.2 +0.3 ! for k-point 6 plot bands between -0.2 and +0.3 a.u. w.r.t Fermi level
End
...
```

After such a run you get a TAPE41 file that you should rename to my.t41, and view with AMSview.

## Induced Density Plots of Response Calculations¶

```
ResponseInducedDensityPlot # Non-standard block. See details.
...
End
```

`ResponseInducedDensityPlot`

Type: Non-standard block Description: Goes together with Restart%ResponseInducedDensityPlot and Grid.

`ResponseInducedDensityPlot (block-type)`

The ResponseInducedDensityPlot block goes together with the `Restart%ResponseInducedDensityPlot`

and `Grid`

keys. In the BAND example directory there is the TD-CDFT for MoS2 Monolayer example that shows how this can be used. Example input:

```
...
Restart
File my_file.rkf
ResponseInducedDensityPlot
End
Grid
Type Coarse
End
ResponseInducedDensityPlot
XCOMPONENT 5 8 ! plot x component of induced densities
! for frequencies number 5 to 8
YCOMPONENT 6 ! plot y component of induced densities
! for frequency number 6
ZCOMPONENT 1 ! plot z component of induced densities
! for frequency number 1
End
...
```

After such a run you get a TAPE41 file that you should rename to my.t41, and view with AMSview.

Attention

The plotting capability works only with response calculation RUNKF files based on the NewResponse method!

## NOCV Orbital Plots¶

```
NOCVOrbitalPlot # Non-standard block. See details.
...
End
```

`NOCVOrbitalPlot`

Type: Non-standard block Description: Goes together with the Restart%NOCVOrbitalPlot and Grid keys. See example.

The NOCVOrbitalPlot blockg oes together with the `Restart%NOCVOrbitalPlot`

and `Grid`

keys. See example PEDANOCV_MgO+CO. Example input:

```
...
Restart
File my_file.rkf
NOCVOrbitalPlot
End
Grid
Type Coarse
End
NOCVOrbitalPlot
1 Band 5 8 ! for k-point 1 plot NOCV Orbitals 5 to 8
End
...
```

After such a run you get a TAPE41 file that you should rename to my.t41, and view with AMSview.

## NOCV Deformation Density Plots¶

```
NOCVdRhoPlot # Non-standard block. See details.
...
End
```

`NOCVdRhoPlot`

Type: Non-standard block Description: Goes together with the Restart%NOCVdRhoPlot and Grid keys. See example.

The NOCVdRhoPlot blockg oes together with the `Restart%NOCVdRhoPlot`

and `Grid`

keys. See example PEDANOCV_MgO+CO. Example input:

```
...
Restart
File my_file.rkf
NOCVdRhoPlot
End
Grid
Type Coarse
End
NOCVdRhoPlot
1 Band 5 8 ! for k-point 1 plot NOCV deformation densities 5 to 8
End
...
```

After such a run you get a TAPE41 file that you should rename to my.t41, and view with AMSview.

## LDOS (STM)¶

The local density of states (LDOS) represents a partial density, (see wikipedia): it is the density arising from states within an energy window.

```
LDOS
DeltaNeg float
DeltaPos float
Shift float
End
```

`LDOS`

Type: Block Description: Local Density-Of-States information. This can be used to generate STM images in the Tersoff-Hamann approximation (see https://doi.org/10.1103/PhysRevB.31.805) `DeltaNeg`

Type: Float Default value: 0.0001 Unit: Hartree Description: Lower bound energy (Shift-DeltaNeg) `DeltaPos`

Type: Float Default value: 0.0001 Unit: Hartree Description: Upper bound energy (Shift+DeltaPos) `Shift`

Type: Float Default value: 0.0 Unit: Hartree Description: The energy bias with respect to the Fermi level.

Integrating from minus infinity (DeltaNeg=1e6) to the fermi level (DeltaPos=0) produces the total (valence) density.

The local density of states is integrated over the resulting interval. Example of an LDOS restart:

```
Restart
File my_file.rkf
DensityPlot
End
Grid
Type Coarse
End
DensityPlot
LDOS
End
LDOS
Shift 0.1
DeltaNeg 0.001
DeltaPos 0.0
End
```

According to this example, we restart from the result file of a previous calculation. The calculation will generate a file TAPE41 which can be viewed with AMSview. (Rename the file to my.t41)

See also Restart, and DensityPlot.

## Electron Energy Density¶

The electron energy density is defined as

\(X(r) = -\left\{ \frac{1}{2} \sum_i^\text{occ} \nabla \psi_i \cdot \nabla \psi_i - V_\text{effective} \rho \right\}\)

It can be obtained by requesting `X`

or `X(fit)`

in a restart, see also Restart, and DensityPlot.

## Save¶

```
Save string
```

`Save`

Type: String Recurring: True Description: Save scratch files or extra data that would be otherwise deleted at the end of the calculation. e.g. ‘TAPE10’ (containing the integration grid) or ‘DensityMatrix’